Rare earth-cobalt metal alloys, developed by 1970, exhibited much greater magnetic energy products and coercivities than previously available with Alnico or ferrite magnets. These alloys were found to be useful in magnetic components requiring miniaturization such as those used in miniature portable stereo headphones and tape players, as well as computers, motors and audio visual components.
With cost and supply problems associated with cobalt, however, another group of alloys based on rare earth-iron-boron compositions were developed during the early 1970's. This alloy is described by Schmidt et al in U.S. Pat. No. 4,612,047 issued Sep. 16, 1986 and by Seon et al in U.S. Pat. No. 4,636,353 issued Jan. 13, 1987. The alloys (e.g., Nd.sub.2 Fe.sub.14 B) exhibit highly desirable magnetic properties for use as permanent magnets.
The commercialization of these rare earth-transition metal alloys has progressed to the point that relatively large quantities of rare earth-transition metal alloy scrap or waste particulates have been generated from the various manufacturing operations used to fabricate the alloys into suitable magnet components, electrical components and the like. The rare earth-transition metal alloy scrap or waste generated by the industries involved varies considerably in form from dry, bulky relatively large scrap pieces to a fine powder or dust referred to as "swarf" usually produced by abrasive grinding and cutting operations employed to fabricate the aforementioned components. Swarf is typically contaminated with grinding media particulates which come from the abrasive wheels and/or belts.
In addition to fabricating rare earth-transition metal alloy (e.g., Nd.sub.2 Fe.sub.14 B and SmCo.sub.5), these same industries may also fabricate traditional magnet alloys such as AlNiCo, and ferrite and the like and thereby also generate large quantities of these types of alloy scrap or waste particulates.
In practice, these different types of alloy scrap or waste particulates oftentimes are disposed of using a common scrap or waste disposal system such that a mixed alloy scrap or waste particulates by-product is generated (i.e., the by-product includes a mixture of different rare earth-bearing alloy particulates along with grinding media particulates). Industries that generate such mixed alloy scrap or waste by-product require some method to dispose of the by-product and to separate and recover the different valuable rare earth metals/alloys present therein.
An object of the present invention is to provide a method of treating a contaminated mixed alloy scrap or waste particulates by-product in a manner to separate and recover discrete metals/alloys present in the mixed by-product.
Another object of the present invention is to provide a method of treating a mixed alloy scrap or waste particulates by-product using combined differential leaching/flotation to separate and recover discrete metals/alloys present in the mixed by-product.